A world I am developing requires that only approximately one quadrasphere or quadrant (1/2 a hemisphere) of the planet be occupied.

I would like the north and south extremes to be outside anything resembling human comfort—far hotter or colder than the daytime Sahara or nighttime South Pole, for instance. There is therefore a single temperate zone, centered somewhere between the pole and the equator, only half of which (divided longitudinally) is habitable.

I don’t have strong opinions about why you can’t go east or west, but it’s a very real barrier, not a misconception or the like.

Total area should ideally be somewhat larger than a quadrant of Earth, but this is a very minor factor if it’s a problem.

Much of the center of the quadrant is taken up by a great sea, such that the large inhabited landmasses extend from the sea out toward the “edge.”

My first thought was to do this with axial tilt, eccentric orbits, things like that. But I realized I simply don’t know nearly enough about such topics as climate science, planetary physics, and so on.

To boil it down:

  1. Is the quadrasphere or quadrant as proposed here possible?

  2. Assuming it is possible, and there is a maximally probable scenario, how would it work?

  3. Insofar as one can predict, what would the various regions outside the quadrasphere or quadrant be like?

NOTE: If there are too many variables here to narrow in on, please itemize these in comments so that I can refine the question.

  • $\begingroup$ What's a quadrasphere? Is this a surface-dwelling world like ours? $\endgroup$
    – JDługosz
    Dec 7, 2015 at 17:26
  • $\begingroup$ See en.m.wikipedia.org/wiki/… $\endgroup$
    – JDługosz
    Dec 7, 2015 at 17:31
  • $\begingroup$ The term is debated, it seems. No standard exists. Other proposals include semihemisphere. Essentially it's 1/4 of the surface, made by slicing a hemisphere crosswise. Thus the US and Canada are in the northwestern quadrasphere. $\endgroup$
    – CAgrippa
    Dec 8, 2015 at 3:53
  • 1
    $\begingroup$ Water world with all significant landmasses located in one quadrasphere? If you have the sea in the center, the land may be the edges of impact crater peeking from the water $\endgroup$
    – MadBender
    Dec 8, 2015 at 8:55
  • 1
    $\begingroup$ @XandarTheZenon It's easiest to ride if you're missing one leg. $\endgroup$
    – CAgrippa
    Mar 22, 2016 at 12:10

1 Answer 1


Make the atmosphere thin, (almost) unbreathable. E.g. the planet lost a lot of atmosphere (or did not have much to begin with). The quadrant is depressed, making it the only place with human tolerable air pressure. An ancient impact could have done it (this also explains the central sea).

  • $\begingroup$ Like on Mars, being confined to Mariner Valley. Feedback between geologic and living processes could operate only in the region and further exaggerate the difference. $\endgroup$
    – JDługosz
    Dec 9, 2015 at 12:30

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